In the electronics industry, a continuing objective is to further and further reduce the size of electronic devices while simultaneously increasing performance and speed. Cellular telephones, personal data devices, notebook computers, camcorders, and digital cameras are but a few of the consumer products that require and benefit from this ongoing miniaturization of sophisticated electronics.
Integrated circuit (“IC”) assemblies for such complex electronic systems typically have a large number of interconnected IC dies (or “chips”). The IC dies are usually made from a semiconductor material such as silicon (“Si”) or gallium arsenide (“GaAs”). Photolithographic techniques are used to form the various semiconductor devices in multiple layers on the IC dies.
After manufacture, the IC dies are typically incorporated into packages that may contain one or several such dies. The IC die is mounted on the surface of a substrate, for example, by means of a layer of epoxy. Bond wires can connect electrical contact points on the upper surface of the IC die to the substrate. Solder contact balls can also be provided on the lower surface of the IC die for additional connections between the IC die and the substrate. A molding compound, typically of molded plastic epoxy such as epoxy molding compound (“EMC”), encapsulates the die and the bond wires, providing environmental protection for the die and defining the semiconductor die package. These die packages or modules are then typically mounted on printed circuit wiring boards.
Due to the ever-decreasing size and ever-increasing density, performance, and speed of such IC dies, the power density (the heat output concentration from the dies) is continually increasing. This requires ever more elaborate designs for thermal management to keep the IC die temperatures within acceptable ranges. Otherwise, and due in part to the poor heat transfer properties of the EMC, the packages are subject to malfunction due to heat build up in the package.
The internal thermal resistance and the thermal performance of a semiconductor package are determined by a series of heat flow paths. By making high heat conductivity connections between the bottom of the die and the substrate within the semiconductor package, heat generated in the die can be transferred efficiently from the die to the substrate. Similarly, by making high heat conductivity connections between the bottom of the semiconductor package and the external substrate on which the semiconductor package is mounted, heat can be transferred efficiently from the substrate within the semiconductor package to the external substrate.
For designs where additional heat must be removed from the semiconductor die, the molding compound that encapsulates the die can be partially omitted from the upper surface of the die to partially expose this surface. The exposed semiconductor die surface can then be put in direct physical contact with a heat spreader that overlies the semiconductor die. To enhance the cooling performance, a layer of thermal grease or the like can be spread between the semiconductor die surface and the heat spreader to improve heat transfer to the heat spreader.
The heat spreader is typically formed so that it can also be attached to the underlying substrate, resulting in a mechanically strong package. Additionally (or alternatively), the heat spreader can be encapsulated in the molding compound that forms the semiconductor package, sometimes with the heat spreader exposed on the upper surface of the package for heat emission therefrom.
The heat thus flows first from the IC die to the body of the semiconductor module or package into which the IC die has been incorporated, and then to the heat spreader. Even though the semiconductor packages interfere with thermal emission from the IC dies, the packages are necessary to protect the IC dies from moisture and mechanical damage. Therefore, an increasingly important consideration in making small, high-speed, high-density devices is providing packages that are capable of adequately spreading the heat generated by the devices.
Consequently, there still remains a need for improved, more economical, more efficient, and more readily manufactured and assembled heat spreader systems, heat spreader packages, and package fabrication systems for use with semiconductor devices. In view of the ever-increasing need to save costs and improve efficiencies, it is more and more critical that answers be found to these problems.
Solutions to these problems have been long sought but prior developments have not taught or suggested any solutions and, thus, solutions to these problems have long eluded those skilled in the art.